Marker bottles, which are ink-filled bottles having a plug with a foam or fabric pad, are popular in bingo halls. The game of bingo involves a game card consisting of an array of numbers, usually from 1 to 75, which are called in random order by the bingo hall operator. Each called number appearing on a player's card is marked off by the player. A marker bottle is a convenient way of marking off numbers called during a game of bingo.
A marker bottle typically comprises a plastic container having a threaded neck and a plug which slip-fits into the neck. The plug includes a top opening covered by or filled with a liquid-permeable pad made from foam, fabric or another permeable material, which allows ink or dye contained in the bottle to be dabbed onto a substrate such as a bingo card. The permeable material controls the flow of ink or dye from the bottle. A threaded closure is typically provided for storing the marker bottle when not in use, to prevent spillage and keep the ink or dye from drying out.
A significant problem is presented by the need to refill the bottle from time to time. The user must grasp the plug and extract it from the neck in order to open the bottle for refilling. However, the plug fits into the neck very snugly to prevent seepage, and the collar of the plug is typically not much wider than the neck of the bottle leaving very little surface for the user to grasp, thus rendering removal of the plug quite difficult. This problem is exacerbated by wet ink or dye from the bottle, which during use seeps onto the plug and makes the plug collar quite slippery and difficult to grasp. Further, ink or dye can creep between the plug and the neck of the bottle, which when dried over time increases the static friction or "stiction" between the plug and the neck and renders removal of the plug even more difficult.